1. Field of the Invention (Technical Field)
The present invention relates to a method and apparatus for a metal roofing system. Particularly, the present invention relates to an improved single ply metal roofing system which permits the use of thicker sheeting than the prior art while solving thermal expansion and contraction issues which plague the prior art systems.
2. Description of Related Art
Known metal roofing systems permit only a maximum thickness of 30 gauge metal-sheeting to be applied to a roof. Such known systems rely on “hat” channel 2 disposed on a roofing substrate, (see prior art FIG. 1). The sheeting is screwed into the hat channel which fixedly holds the sheeting in place and prevents if from moving. Securing the sheeting to an inflexible member, such as a hat channel, prevents the sheet metal from being able to expand and contract with thermal cycling. Thermal expansion and contraction forces on the sheeting increase as the thickness of the metal increases. Accordingly, known systems cannot apply thicker and more substantial sheeting because thermal expansion and contraction occurs which results in excessive expansion and contraction of the metal. The excessive expansion and contraction of such metal-sheeting results in excessive forces being applied to the fasteners that are driven through it. These excessive forces cause the fasteners to either become loose or cause the sheeting to pull away from the fasteners; either of these scenarios results in a loose fit between the fastener and the sheeting, thus permitting water to pass between the fastener and the sheeting, thereby breaching the surface of the roof.
Because the known metal roofing systems are limited to a maximum thickness of only about 30 gauge, those systems are easily punctured. For example, puncturing may occur by a worker simply dropping a screwdriver during installation or dropping a tool while performing any other work on a roof, i.e. repairing a heating, ventilation, and air conditioning unit. Accordingly, a quick patch is not at all uncommon and such patches themselves often result in point of water entry several years later.
Yet another problem with known single ply roofing systems is that the roofing sheets are held to the top of the structure by screwing the edges of the roofing sheets onto hat channels that are disposed on the top of the structure. The hat channels themselves are modified, non-flexible, channel-iron members which rigidly and fixedly hold the roofing sheets in place. When the roofing sheets expand and contract, because their edges are held firmly held in place, the roofing sheets must thus bow up in their central region. This continuous rising and falling of the central portion of each of the sheets in response to thermal expansion and contraction, coupled with the row of fasteners around the periphery thereof, results in metal fatiguing of the roofing sheets along the inside edge of the metal fasteners. Over time, the constant cycling of thermal contractions and expansions thus causes the breaks in the roofing sheets which thus enables water to breach the roofing surface. Because even thicker roofing sheeting experiences even greater expansion and contraction cycles, attempts to secure thicker sheeting to the known hat channels results in even more extreme rising and falling of the central portion of the sheets in response to the thermal expansions and contractions. This extreme rising and falling of the sheets results in metal fatiguing of the roofing sheeting in a much more rapid manner than what is typical.
Although insulating sheeting can and often is applied between the hat channels immediately below the roofing sheeting, the space beneath the hat channels typically remains un-insulated. Because the air within the un-insulated metal hat channels is exposed to warm and cold temperature cycles, condensation often forms along the inside of the hat channels. This condensation often results in non-protected metal surfaces rusting (i.e. the fasteners that are driven through the hat channels and which hold the sheeting thereto). The rusting of the very components that hold the metal roofing structures together is obviously a very undesirable quality in the known metal roofing structures.
Known metal roofing systems also provide undesirable flashing. This is because the flashing that is used to trim outer portions of known roof structures do not have an interlocking structure that adequately prevents water from blowing, splashing, or otherwise traveling therebetween, thus resulting in water breaching the roofing surface. Known metal roofing systems typically rely on a two-piece flashing arrangement wherein the upper portion of the flashing extends slightly beyond the lower portion. This simple overlap joint does not provide an effective seal in all instances.
There is thus a present need for a single ply metal roofing system which permits a thicker sheeting to be applied and which avoids metal fatiguing of the roofing sheeting and which further avoids the use of metal structures that permit condensation to form therein. There is also a present need for a metal roofing system that provides flashing which effectively prevents splashing and wind-driven rain from breaching the roof surface. There is yet another present need for a metal roofing system that more adequately resists puncturing of sheet metal while it is being installed and while other roof work is subsequently performed.